Power conversion apparatus, power generation system, controller, and method for performing control

1. A power conversion apparatus comprising: a power converter configured to convert supplied power supplied from a power generation source into second power; a target command controller configured to increase or decrease a target command so as to cause the supplied power to follow maximum suppliable power of the power generation source; a feedback controller configured to control the power converter by feedback control that is based on a deviation between the target command and at least one of a supplied voltage and a supplied current supplied from the power generation source to the power converter; and a gain adjustor configured to adjust a gain of the feedback control based on at least one of the supplied voltage, the supplied current, and the target command, wherein the target command controller is configured to, when determining that the supplied power has reached a maximum point, output to the feedback controller a non-following target command that does not follow a change in the supplied power, instead of outputting the target command to maximize the supplied power.

2. The power conversion apparatus according to claim 1 , wherein the gain adjustor is configured to adjust the gain of the feedback control based on at least one of an equation and a table that correlate the gain of the feedback control with at least one of the supplied voltage, the supplied current, and the target command.

3. The power conversion apparatus according to claim 1 , wherein the gain of the feedback control comprises a first gain at a time when the supplied voltage is higher, and a second gain at a time when the supplied voltage is lower, and wherein the gain adjustor is configured to make the first gain larger than the second gain.

4. The power conversion apparatus according to claim 1 , wherein the gain of the feedback control comprises a third gain at a time when the supplied current is higher, and a fourth gain at a time when the supplied current is lower, and wherein the gain adjustor is configured to make the third gain larger than the fourth gain.

5. The power conversion apparatus according to claim 1 , wherein the gain adjustor is configured to make the gain of the feedback control larger as the supplied voltage becomes higher or the supplied current becomes lower.

6. The power conversion apparatus according to claim 5 , wherein the power generation source comprises a solar cell, and wherein the gain adjustor is configured to adjust the gain of the feedback control based on an amount of solar radiation to the solar cell.

7. The power conversion apparatus according to claim 1 , wherein the gain adjustor is configured to set a first control gain for a part of the feedback control that is before the supplied voltage or the supplied current becomes a voltage or a current corresponding to the maximum suppliable power, wherein the gain adjustor is configured to set a second control gain for another part of the feedback control that is after the supplied voltage or the supplied current has become the voltage or the current corresponding to the maximum suppliable power, and wherein the gain adjustor is configured to make the first control gain larger than the second control gain.

8. The power conversion apparatus according to claim 1 , wherein the feedback controller comprises a command generator configured to perform at least one of P control, PI control, PID control, and PD control with respect to a difference between the target command and at least one of the supplied current and the supplied voltage, and a drive controller configured to generate, based on an output from the command generator, a drive signal to drive the power converter, wherein the gain of the feedback control comprises at least one of a proportional gain, a proportional integration gain, a proportional integration differentiation gain, and a proportional differentiation gain of the command generator.

9. The power conversion apparatus according to claim 1 , wherein the feedback controller is configured to control an output of the power converter based on a power command that is based on a power supply characteristic of the power generation source.

10. The power conversion apparatus according to claim 9 , wherein the target command generated by the target command controller comprises a voltage command, and wherein the feedback controller comprises a command generator configured to generate a current command based on the supplied voltage and the voltage command, a power command generator configured to generate the power command based on the current command or the supplied current and based on the voltage command or the supplied voltage, an output current command generator configured to generate an output current command based on the power command, and a drive signal generator configured to generate, based on the output command, a drive signal to drive the power converter.

11. The power conversion apparatus according to claim 9 , wherein the target command generated by the target command controller comprises a current command, and wherein the feedback controller comprises a command generator configured to generate a voltage command based on the supplied current and the current command, a power command generator configured to generate the power command based on the voltage command or the supplied voltage and based on the current command or the supplied current, an output command generator configured to generate an output current command based on the power command, and a drive signal generator configured to generate, based on the output current command, a drive signal to drive the power converter.

12. The power conversion apparatus according to claim 1 , further comprising a deviation determiner configured to determine whether at least one of the supplied voltage and the supplied current is larger than the target command by a predetermined value, wherein when the deviation determiner has determined that at least one of the supplied voltage and the supplied current is larger than the target command by the predetermined value, the target command controller is configured to set the target command at a value that is based on at least one of the supplied voltage and the supplied current.

13. The power conversion apparatus according to claim 1 , wherein the target command controller comprises a first target command controller configured to output the target command to maximize the supplied power, a second target command controller configured to output a non-following target command that does not follow the change in the supplied power, a first determiner configured to determine whether the supplied power has reached the maximum point, an output switch configured to, when the first determiner has determined that the supplied power has reached the maximum point, output to the feedback controller the non-following target command of the second target command controller instead of the target command of the first target command controller, and a second determiner configured to determine whether the supplied power is larger when the non-following target command of the second target command controller is output to the feedback controller than the supplied power determined by the first determiner to have reached the maximum point.

14. The power conversion apparatus according to claim 13 , wherein after the output switch has output the non-following target command of the second target command controller to the feedback controller, the output switch is configured to resume outputting the target command of the first target command controller to the feedback controller, and wherein when the second determiner has determined that the supplied power is larger when the non-following target command of the second target command controller is output to the feedback controller than the supplied power determined by the first determiner to have reached the maximum point, the first target command controller is configured to make the resumed target command a command that is based on the non-following target command of the second target command controller.

15. The power conversion apparatus according to claim 1 , wherein the target command controller includes an output switch and is connected to the feedback controller via the output switch, the output switch outputting to the feedback controller the non-following target command instead of outputting the target command, when determining that the supplied power has reached the maximum point.

16. A power generation system comprising: a power generation source; and a power conversion apparatus comprising: a power converter configured to convert supplied power supplied from the power generation source into second power, a target command controller configured to increase or decrease a target command so as to cause the supplied power to follow maximum suppliable power of the power generation source, a feedback controller configured to control the power converter by feedback control that is based on a deviation between the target command and at least one of a supplied voltage and a supplied current supplied from the power generation source to the power converter, and a gain adjustor configured to adjust a gain of the feedback control based on at least one of the supplied voltage, the supplied current, and the target command, wherein the target command controller is configured to, when determining that the supplied power has reached a maximum point, output to the feedback controller a non-following target command that does not follow a change in the supplied power, instead of outputting the target command to maximize the supplied power.

17. A controller comprising: a target command controller configured to increase or decrease a target command so as to cause supplied power supplied from a power generation source to a power converter to follow maximum suppliable power of the power generation source; a feedback controller configured to control the power converter by feedback control that is based on a deviation between the target command and at least one of a supplied voltage and a supplied current supplied from the power generation source to the power converter; and a gain adjustor configured to adjust a gain of the feedback control based on at least one of the supplied voltage, the supplied current, and the target command, wherein the target command controller is configured to, when determining that the supplied power has reached a maximum point, output to the feedback controller a non-following target command that does not follow a change in the supplied power, instead of outputting the target command to maximize the supplied power.

18. A method for performing control, the method comprising: increasing or decreasing a target command so as to cause supplied power supplied from a power generation source to a power converter to follow maximum suppliable power of the power generation source; controlling the power converter by feedback control that is based on a deviation between the target command and at least one of a supplied voltage and a supplied current supplied from the power generation source to the power converter; adjusting a gain of the feedback control based on at least one of the supplied voltage, the supplied current, and the target command; and when determining that the supplied power has reached a maximum point, outputting a non-following target command that does not follow a change in the supplied power, instead of outputting the target command to maximize the supplied power.